The present invention generally relates to a light emitting diode (“LED”) grow light system. More specifically, the present invention relates to an LED grow light system including an LED having a filter substrate and/or a filter coating thereon for at least partially reflecting and/or absorbing blue light spectra to mimic a High Pressure Sodium (“HPS”) comparable light spectrum for deployment as a replacement plant grow light.
In the last several decades, High Pressure Sodium (“HPS”) lamps have been used extensively as plant grow lights for indoor plant growing systems and are proven to be some of the best available artificial lighting systems for plant growth. HPS lamps are particularly conducive for use in plant growing systems because of the relatively high output intensity within certain visible light spectrums, their relatively low price, long life, high photo-synthetically active radiation (“PAR”) emission, and high electrical efficiency. Although, one drawback is that HPS lamps are not necessarily optimal for promoting photosynthesis and photomorphogenesis. For example, FIG. 1 is an HPS light spectrum graph 20 illustrating the relative intensities of visible light emitted from an HPS lamp. As shown, the HPS lamp has an energy intensity that is strongest around the orange-red part of the spectrum (i.e., at wavelengths of about 580-620 nanometers (“nm”)). Such strong light intensities in this range tend to stimulate plant hormones to start budding and flowering, but do not necessarily promote desired growth. Thus, one disadvantage is that continued exposure to such high intensities in the orange-red part of the spectrum (i.e., wavelengths of about 580-620 nm) can result in excessive leaf and stem elongation due to the unbalanced spectral emission intensity from the HPS lamp in this range, and especially relative to other absorption peaks of the plant. Thus, while HPS lamps have been widely used, plant growth under HPS lamps may be less than optimal.
In recent years, LED lighting technology has matured within the lighting industry such that advancements in LED architecture have resulted in significantly reducing manufacturing costs, increasing LED efficiency, and creating an overall more robust LED light design better suited for use in plant grow light systems. In this respect, it may now be feasible to replace HPS lamp-based plant grow light systems with LED-based plant grow light systems in the horticulture business to lower the Total Cost of Ownership (“TCO”), such as lowering the cost of electricity (i.e., LEDs tend to be more energy efficient than HPS lamps), lowering the cost of air conditioning (i.e., LEDs tend to generate less heat than HPS lamps), lowering the cost of the lamps themselves, and increasing lamp longevity (i.e., decreasing the replacement rate in view that LEDs have a longer projected lifespan). Although, one major drawback of using LEDs as a plant grow light is that the spectrum of the LED output is different than the output of HPS lamp. For example, LED grow light designs manufactured specifically for the horticulture market use blue LEDs (e.g., at wavelengths of about 420-480 nm) and red LEDs (e.g., at wavelengths of about 620-780 nm). To this end, the green spectrum (e.g., at wavelengths of about 500-580 nm) is commonly omitted from LED plant grow lights since the belief within the industry is that green leaves reflect green light and, therefore, the green spectrum is not absorbed by the plant and consequently unnecessary. Thus, important aspects of robust plant growth are lost since wavelengths between the blue spectrum and red spectrum (e.g., within the green or yellow spectrums) are disregarded and commonly omitted from LED grow lights. HPS lamps, on the other hand, have relatively stronger (yet not optimal) green spectrum intensities in the 500-580 nm wavelength range as shown, e.g., in FIG. 1. Although, HPS lamps are more expensive and have a relatively shorter life when compared to LED lights, and HPS lamps are also not necessarily environmentally friendly because they contain mercury, and, importantly, the spectrum of the HPS lamp cannot be tailored to meet the various spectral needs of different plants.
One benefit of an LED grow light is that there are a wide number of available LEDs that generate light output at custom wavelengths. Although, mimicking the HPS lamp in an LED grow light is not as simple as aggregating several differently colored industry standard LEDs having different light output wavelengths because the resultant spectrum is not exactly similar to that of the HPS lamp light spectrum graph 20 illustrated with respect to FIG. 1. For example, FIG. 2 is a tri-LED light spectrum graph 22 illustrating the relative radiant power of three off-the-shelf LEDs having different color temperatures (“CCT”) and different color rendering indices (“CRI”). As shown, even the lowest 2,200K CCT LED does not have a spectrum that matches the HPS lamp light spectrum graph 20 as closely in intensity in the blue spectrum (e.g., at wavelengths of about 420-480 nm)—the relative radiant power intensity is too high. It becomes necessary to either increase the amount of the orange/red light (e.g., at wavelengths of about 580-620 nm) to compensate for the relatively high intensity in the blue spectrum or decrease the amount of blue light so the LED light output is similar to that of the HPS lamp. Continuing to lower the CCT of the LED further lowers the amount of blue light, but at a penalty in lowering the efficiency of the LED. Thus, current LEDs known in the art are ineffective in grow light applications, especially when compared to HPS lamps.
In another example, FIG. 3 illustrates an octo-LED light spectrum graph 24 illustrating the relative radiant power of eight standard off-the-shelf LEDs, each with a different center light output wavelength. Here, to add more of the orange/red spectrum to the LED lighting system, additional LEDs that emit output light in more of the amber, orange/red, and/or red spectrum may be added to help better mimic the spectrum of that of the HPS lamp. This is accomplished chiefly by increasing the output intensity of the LEDs having the orange/red wavelengths, such as relative to the blue spectrum light output. Even so, each of the LEDs produces sharp peaks uncharacteristic of the HPS lamp light spectrum graph 20 and natural light, thus producing less than optimal plant growth results.
Other more recent LED plant grow light technologies claim to generate light at wavelengths all along the visible color spectrum under computer control (as needed), but these grow light systems still fail to emphasize the importance of the relative intensities of the HPS lamp output spectrum, such as shown with respect to FIG. 1. Thus, the potential benefits of using LEDs as a replacement for HPS lamps (e.g., lower cost and higher efficiency) for use as a plant grow light has yet to be achieved in the horticulture industry. While there are numerous studies currently underway examining the effects of wavelengths on plant growth, those features are still in the experimental stages and many benefits are still unknown. Thus, adoption rate in the industry may be slow. Relatively smaller growers may begin using LEDs as plant grow lights as early adopters to try and benefit from reductions in TCO; although such small growers are still burdened with the changes during the growth cycle of the plants. That is, the growers must make adjustments in the light spectrum during the plant growth cycle, and sometimes such adjustments fail. Relatively larger-scale growers have generally avoided such risk. Thus, industry wide transition from HPS lamp systems to LED lamp-based systems for use as plant grow lights has taken some time.
There exists, therefore, a significant need in the art for an LED grow light system suitable as a replacement of for an HPS lamp, wherein such an LED grow light system includes and LED having a phosphor layer positioned underneath a filter substrate or filter coating having reflective or absorptive properties limiting the output of blue spectra on par with an HPS lamp and emphasizing emission of intermediate spectra in the green/yellow spectra range to enhance plant growth. Such an LED grow light system should be readily interchangeable with the HPS lamp to promote industry wide adoption. The present invention fulfills these needs and provides further related advantages.